1. Field of the Invention
This invention relates to fluid temperature sensors and in particular to sensors for use in determining the temperature of a sterile injectate fluid.
2. Description of the Prior Art
In one known fluid temperature sensor manufactured by Thermometrics Inc., of Edison, N.J., a thermistor temperature sensor is located in the midportion of a clear plastic tube. The thermistor is permanently attached to the device and is electrically isolated from the fluid in the lumen of the tube by means of a thermoplastic protective sleeve. The lead wires from the thermistor are connected to an electrical connector located on the side of the tube. A problem arises in the use of such a temperature sensor in that it is difficult to resterilize the device for use with a second patient. Further, the relatively expensive thermistor must be discarded with the tube in the event the tube becomes damaged.
Another form of mass flowmeter catheter is illustrated in U.S. Pat. No. 3,545,428, of Wilton W. Webster, Jr., to have two concentric lumens, with means coupled to the posterior end of the outer lumen for injecting coolant liquid. A pair of electrical temperature sensing devices is associated with the device.
In U.S. Pat. No. 3,561,266, Michael Auphan et al disclose another device for measuring the flow velocity of a fluid, such as the rate of flow of blood in a human body. The device includes first and second paraxial tubes insertable into the patient's blood vessel for injecting a serum miscible with the blood and for removing a sample of the blood serum mixture respectively. Means are provided for measuring the velocity of the serum and the temperature of the serum, the blood, and the blood serum mixture. An electromagnetic agitator is provided for mixing the blood and the serum.
In U.S. Pat. No. 3,595,079 of Allen R. Grahn, a fluid flow velocity measuring apparatus is disclosed, including a probe having fluid flow velocity and temperature sensor thermistors thereon. The probe is adapted to be inserted into a fluid flow conduit. The device includes circuit means for maintaining the velocity sensor thermistor at a predetermined temperature differential relative to the temperature of the fluid being measured. The probe further includes a flow direction sensor thermistor adjacent the velocity sensor thermistor.